I have been playing with Google Wave thanks to an invitation from Lucian.
I have enjoyed working with it. My only technical complaint is that chaning into the settings wave seemed quite slow. (and making everything be inside a wave seems perhaps wave overkill.)
On first impression I think this idea would be good for a team communication / collaboration tool.
At present there are so few people signed up, that communication is slower than via email. (You have to login to check your waves, and at present it may be just another place to loging and check for messages.)
We will all have to keep an eye on this technology and see how it develops, and how many people stat to use it.